Simon M. Scott

Total luminescence spectroscopy with pattern recognition for classification of edible oils

Total luminescence spectroscopy combined with pattern recognition has been used to discriminate between four different types of edible oils, extra virgin olive (EVO), non-virgin olive (NVO), sunflower (SF) and rapeseed (RS) oils. Simplified fuzzy adaptive resonance theory mapping (SFAM), traditional back propagation (BP) and radial basis function (RBF) neural networks provided 100% classification for 120 samples, SFAM was found to be the most efficient. The investigation was extended to the adulteration of percentage v/v SF or RS in EVO at levels from 5% to 90% creating a total of 480 samples. SFAM was found to be more accurate than RBF and BP for classification of adulterant level. All misclassifications for SFAM occurred at the 5% v/v level resulting in a total of 99.375% correctly classified oil samples. The percentage of adulteration may be described by either RBF network (2.435% RMSE) or a simple Euclidean distance relationship of the principal component analysis (PCA) scores (2.977% RMSE) for v/v RS in EVO adulteration.

Microfluidic Bioreactors for Cell Culturing: A Review

The use of microfluidic bioreactor platforms for cell culturing holds considerable promise for a range of fields which include drug discovery, tissue engineering, bioprocessing optimisation and cell based screening studies. Microflu- idic bioreactor systems have length scales that are well matched to the physical dimensions of most cells and microorgan- isms. In view of this, microfluidic bioreactors have attractive features which make them ideal to study the behaviour of cells and their internal organisation in their native microenvironment. Due to their small footprint microbioreactor plat- forms offer a number of advantages over conventional macroscale systems including improved biological function, higher quality cell-based data, reduced volume of reagents, ease of integration and lower cost. This review highlights the basic concepts, designs and operational requirements of microbioreactors for cell based studies. An illustrative outline of differ- ent applications of microbioreactors and some indication of new trends and progress in recent years are provided. Specific examples of applications of microbioreactors are drawn for cytotoxicity assays, tissue engineering, stem cells, microbial fermentations, single cell analysis and in vitro fertilisation.

Classification of fresh edible oils using a coated piezoelectric sensor array-based electronic nose with soft computing approach for pattern recognition

An electronic nose based on an array of six bulk acoustic wave polymer-coated piezoelectric quartz (PZQ) sensors with soft computing-based pattern recognition was used for the classi-fication of edible oils. The electronic nose was presented with 346 samples of fresh edible oil headspace volatiles, generated at 45°C. Extra virgin olive (EVO), nonvirgin olive oil (NVO) and sunflower oil (SFO) were used over a period of 30 days. The sensor responses were visualized by plotting the results from principal component analysis (PCA). Classification of edible oils was carried out using fuzzy c-means as well as radial basis function (RBF) neural networks both from a raw data and data after having been preprocessed by fuzzy c-means. The fuzzy c-means results were poor (74%) due to the different cluster sizes. The result of RBF with fuzzy c-means preprocessing was 95% and 99% for raw data input. RBF networks with fuzzy c-means preprocessing provide the advantage of a simple architecture that is quicker to train.

Low cost microfluidic cell culture array using normally closed valves for cytotoxicity assay.

A reusable low cost microfluidic cell culture array device (MCCAD) integrated with a six output concentration gradient generator (cGG) and 4×6 arrays of microchamber elements, addressed by a series of row and columnar pneumatically actuated normally closed (NC) microvalves was fabricated for cell-based screening of chemotherapeutic compounds. The poly(dimethylsiloxane) (PDMS) device consists of three layers: fluidic, control and membrane which are held by surface contact and made leak-proof by clamping pressure. The NC valves are actuated by a thick PDMS membrane that was created by a novel method based on the self-assembly of PDMS pre-polymer molecules over a denser calcium chloride solution. The membrane actuated the valves reliably and particulates such as alumina particles (3 µm) and MCF-7 cells (20-24 µm) (2×10(5) cells/mL) were flowed through the valves without causing blockage or leakage and consequently avoiding contamination of the different cell culture elements. The MCCAD was cast and assembled in a standard laboratory without specialist equipment and demonstrated for performing quantitative cell-based cytotoxicity assays of pyocyanine on human breast cancer (MCF-7) cells and assessed for toxic effect on human hepatocyte carcinoma (HepG2) cells as an indicator for liver injury. Then, the MCCAD was demonstrated for sequential drug combinatorial screening involving gradient generation of paclitaxel doses followed by treatment with aspirin doses on the viability of MCF-7 cells. The interaction between paclitaxel and aspirin was evaluated by using the Bliss independence predictive model and results showed reasonable agreement with the model. A robust, portable, easily fabricated and low cost device is therefore shown to conveniently carry out culturing of multiple cell lines for high throughput screening of anti-cancer compounds using minimal reagents.

Discrimination of Sri Lankan black teas using fluorescence spectroscopy and linear discriminant analysis.

BACKGROUND The quality of teas is currently graded using trained tea tasters, whose evaluation can sometimes be subjective. In this study the simple fluorescence-based technique of total luminescence spectroscopy (TLS) in conjunction with data classification using principal component analysis (PCA) was applied to discriminate between teas from 11 different Sri Lankan plantations. Solvent extraction of the tea samples was followed by TLS to record excitation-emission matrices in the excitation range 250-590 nm and emission range 300-700 nm. RESULTS The application of PCA and linear discriminant analysis (LDA) allowed the successful classification of all 11 teas using only the first two principal components. LDA demonstrated how the technique was able to discriminate between all teas correctly with 100% classification. CONCLUSION Further development of this work could lead to a simple device that could be used by tea manufacturers instead of or alongside trained tea tasters to grade teas.

Cavity Enhanced Immunoassay Measurements in Microtiter Plates using BBCEAS

We report on the first detailed use of broadband cavity enhanced absorption spectroscopy (BBCEAS) as a detection system for immunoassay. A vertical R ≥ 0.99 optical cavity was integrated with a motorized XY stage, which functioned as a receptacle for 96-well microtiter plates. The custom-built cavity enhanced microplate reader was used to make measurements on a commercially available osteocalcin sandwich ELISA kit. A 30-fold increase in path length was obtained with a minimum detectable change in the absorption coefficient, αmin(t), of 5.3 × 10(-5) cm(-1) Hz(-1/2). This corresponded to a 39-fold increase in the sensitivity of measurement when directly compared to measurements in a conventional microplate reader. Separate measurements of a standard STREP-HRP colorimetric reaction in microtiter plates of differing optical quality produced an increase in sensitivity of up to 115-fold compared to a conventional microplate reader. The sensitivity of the developed setup compared favorably with previous liquid-phase cavity enhanced studies and approaches the sensitivity of typical fluorometric ELISAs. It could benefit any biochemical test which uses single pass absorption as a detection method, through either the label free detection of biologically important molecules at lower concentrations or the reduction in the amount of expensive biochemicals needed for a particular test, leading to cheaper tests.

Gas-phase pre-concentration for a quartz crystal microbalance based electronic nose

The effect of different relative humidity (RH) on the response of a six-polymer coated Quartz Crystal Microbalance (QCM) sensor based electronic nose (EN) was investigated, RH 30 and 50% respectively. Increases in the sensor responses were observed for an increase in RH. A stainless steel pre-concentration tube (PCT) containing Porapak-S and a nichrome heating element was developed to minimise the effect and allow for chromatographic pre-separation. Breakthrough times of chemical compounds through the PCT were experimentally determined and used to select a mixture of water and toluene as a suitable sample for pre-separation. The PCT was capable of separating the water from the toluene and the EN was competent at evaluating the concentration of toluene in the solution.

Replication of micro-feature using variety of polymer and commonly used mould at elevated temperature and pressure

Due to the functional dependency of micro-systems technologies on stringent dimensions, masses and tolerances, strict quality requirement is paramount for mass producing micro-parts for use in micro-devices. The consistency of components produced could vary as a result of significant effects of process parameters or process noise, thereby necessitating the urge for experimental studies to determine the best process combination that will produce a variant free component that will meet the dimension, mass and other parameters requirement of its application use. In this paper, the influence of some process parameters on replication of micro-feature is explored. Parts with micro-feature designed are moulded using polyethylene and polypropylene. Design of experiment (DoE) approach was applied to correlate the fabricated parts quality to the processing parameters. Two level, half factorial 8-run (24-1) experimental plan was used to investigate the effect of four process parameters of melt temperature, injection pressure, mould temperature and holding time on the replicated quality of the moulded parts, with part mass as output parameter to reflect variability. Of all the investigated process parameters, result of experiment indicated melt temperature and holding time as most statistical significant processing parameter for parts produced using polypropylene. While there are no statistically significant effects of process parameters for those parts produced using polyethylene, rather, variability is observed to have occurred as a result of process noise. Furthermore, the experiments show that variability in the response parameter during micro-injection moulding differs for different polymer. Therefore, appropriate polymer type should as well be made to match with suitable processing parameters so as to obtain quality replication of micro-feature when mass producing.

Microbioreactor Integrated with a Sensor for Monitoring Intracellular Green Fluorescence Protein (GFP)

A prototype Polydimethylsiloxane (PDMS) based microbioreactor integrated with a photodiode detector for monitoring intracellular green fluorescent protein ultraviolet (GFPUV) expression is described. The developed system is compact, simple and inexpensive thus making it ideal for an economical on chip detection of intracellular GFP and other biological applications. The detection limit for cell free GFPUV was found to be 4.8 ×10− 8 M while for Fluorescein isothiocyanate (FITC) was found to be 1.2 ×10− 6 M. The performance of the photodiode detector was benchmarked with a CCD spectrophotometer and results showed favorable comparison. This study demonstrates the quest to develop integrated microsystems that can be used to monitor cellular dynamics in real time.

Fabrication of Microfluidic Devices for Forensic Molecular Diagnostics

There have been considerable advances in the development of microfluidic devices that can carry out the automated and sophisticated processing necessary for DNA analysis and forensic biology. Polymer substrates with high replication techniques are often used in the manufacture of microfluidic devices that are single use, low cost and disposable. High replication techniques require the creation of a master mould from which the devices are subsequently fabricated. This review will describe the use of high replication techniques for device fabrication, with a focus on creation of the master mould manufacture and application of these devices in molecular diagnostics for forensic applications.